1. Field of the Invention
The present invention relates to a magnetic random access memory including conductive layers each formed of a refractory metal.
2. Description of the Related Art
In a spin injection magnetization reversal type magnetic random access memory (MRAM), annealing must be performed at a high temperature of 350° C. or above in order to improve crystallinity of MgO in a tunnel insulating film and thereby increase the magnetoresistive ratio. Further, in some expected magnetic materials, especially perpendicular magnetic materials, an annealing temperature of approximately 500 to 700° C. is required to improve characteristics.
However, in an interconnect structure assumed in a magnetic random access memory, a current is large in both current generation magnetic field writing and spin injection writing, and using an Al interconnect or a Cu interconnect has been conventionally premised. In such a structure, when high-temperature annealing at 500 to 700° C. is carried out after forming a magnetic tunnel junction (MTJ) film, reliability of a device is highly possibly degraded due to, e.g., occurrence of interfacial diffusion of a contact and a substrate.
It is to be noted that the following documents of reference information of conventional technologies are present in relation to the present invention.    [Patent Document 1] JP-A 2003-282837 (KOKAI)    [Patent Document 2] JP-A 2003-133527 (KOKAI)    [Patent Document 3] Specification in U.S. Patent Application Laid-open No. 2006/0002184    [Patent Document 4] JP-A 2004-214459 (KOKAI)